1. Field of the Invention
The present invention relates to a lens apparatus attachable to a camera body, a camera system including the lens apparatus, and a camera having an optical image stabilizing unit for reducing an image shake caused by vibrations, such as a camera shake.
2. Description of the Related Art
Japanese Patent Application Laid-Open No. 8-184870 discusses an optical apparatus having an optical image stabilizing unit for reducing image blurring caused by vibrations, such as camera shake.
The optical apparatus discussed in Japanese Patent Application Laid-Open No. 8-184870 has an image stabilizing unit supported by an elastic member. In this optical apparatus, a locking mechanism for fixing the image stabilizing optical unit, when an image stabilization operation is off, is unnecessary.
In this optical apparatus, the elastic force of the elastic member is set to cancel the self-weight of the image stabilizing unit. Thus, the image stabilizing unit is set to align with an optical axis when an image stabilization operation is off.
Generally, the optical performance (or lack of optical aberration) of a photographic optical system is basically designed to be best under the condition where the optical axis is not bent. Accordingly, the larger a deviation angle to the optical axis (i.e., an inclined angle of an exit light axis to an incident light axis) becomes, the greater the degradation of an image, such as chromatic aberration or reduction of marginal luminance, increases.
Therefore, to obtain the best optical performance, preferably, the image stabilizing optical unit is held as close to the optical axis as possible by increasing the elastic force of the elastic member to decrease an amount of drop of the image stabilizing optical unit due to the self-weight thereof.
In view of electric power saving, there is a conflicting demand to decrease the elastic force for decreasing the driving force needed to move the image stabilizing optical unit.
Japanese Patent Application Laid-Open No. 7-199263 (corresponding to U.S. Pat. No. 6,064,826) discusses a change of the driving range in a direction perpendicular to an optical axis of an image stabilizing optical unit according to a focal length of a photographic optical system.
However, the apparatuses respectively discussed in Japanese Patent Application Laid-Open No. 7-199263 and Japanese Patent Application Laid-Open No. 8-184870 do not consider the posture change of a camera (e.g., a posture change between a portrait orientation and a landscape orientation). Thus, the image stabilizing optical unit may greatly deviate from an optical axis position. Accordingly, there may occur an inappropriate image stabilizing operation.